Physics and Chemistry of the Earth 89–90 (2015) 46–55 Contents lists available at ScienceDirect Physics and Chemistry of the Earth journal homepage: www.elsevier.com/locate/pce Expansion of agricultural oasis in the Heihe River Basin of China: Patterns, reasons and policy implications ⇑ Wei Song a, , Ying Zhang b a Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China b Chinese Academy of Surveying and Mapping, 28 Lianhuachi West Road, Haidian District, Beijing 100830, China article info abstract Article history: The Heihe River Basin (HRB) is the second largest inland river basin in the arid region of northwestern Received 11 March 2015 China. An agricultural oasis is a typical landscape in arid regions providing precious fertile soil, Received in revised form 17 June 2015 living space and ecological services. The agricultural oasis change has been one of the key issues in sus- Accepted 11 August 2015 tainable development in recent decades. In this paper, we examined the changes in the agricultural oasis Available online 24 August 2015 in HRB and analyzed the socio-economic and climatic driving forces behind them. It was found that the agricultural oasis in HRB expanded by 25.11% and 14.82% during the periods of 1986–2000 and 2000– Keywords: 2011, respectively. Most of the newly added agricultural oases in HRB were converted from grassland Agricultural oasis (40.94%) and unused land (40.22%). The expansion in the agricultural oasis mainly occurred in the middle Land-use change Driving forces reaches of HRB, particularly in the counties of Shandan, Minle, Jinta and Jiuquan city. Changes in the rural Panel data model labor force, annual temperature and precipitation have significant positive effects on agricultural oasis The Heihe River Basin changes, while the ratio of irrigated agricultural oases has significant negative effects on agricultural oasis changes. The agricultural oasis expansion in HRB is the combined effect of human activity and climate change. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction foundation of the People’s Republic of China in 1949, as well as the implementation of reform and the opening-up policy in 1978, Arid and semi-arid regions cover more than 30% of the land on the economy in China developed rapidly, inducing the evolution the earth’s surface (Okin et al., 2006) and 22% of the land area in in agricultural oases. The evolution of agricultural oases has two China (Bai et al., 2014). An oasis is a unique intrazonal landscapes opposite processes: oasification and desertification (Li et al., existing within arid and semi-arid regions, which allows flourish- 2006; Su et al., 2007; Zhang et al., 2003). Agricultural oasification ing vegetation and human settlement due to a stable water supply usually means the expansion of an agricultural oasis, i.e. convert- (Ling et al., 2013). Although an oasis covers less than 5% of the total ing the desert to an agricultural oasis under the combined effects area in arid and semi-arid regions in China, it holds more than 90% of human activities and climate change (Xie et al., 2014). Desertifi- of the population and 95% of social wealth in these regions (Wang cation usually means the degradation of an agricultural oasis, i.e. et al., 2008). An oasis not only provides precious fertile soil and liv- converting an agricultural oasis into a desert (Chen et al., 2014; ing space for human beings in the barren desert, but also regulates Liu et al., 2010b; Pan and Li, 2013; Zhang et al., 2008). the regional climate by the vegetation and water resources within The expansion of an agricultural oasis can increase the total it. Therefore, the oasis ecosystem directly influences the environ- crop yields and promote humans’ well-being to some degree. mental and social security in arid and semi-arid regions. The oasis However, the scale of an agricultural oasis is not necessarily ‘‘the change has been one of the key issues in the sustainable develop- larger the better” (Ling et al., 2013). Water is a vital limiting factor ment in recent decades (Cheng et al., 2006). for sustainable crop production and social development in arid and An agricultural oasis is defined as cultivated land that can be semi-arid regions (Jia et al., 2004). The expansion of an agricultural irrigated by human activities (Bai et al., 2014). Since an agricultural oasis will inevitably increase the water demand due to irrigation oasis can provide the necessary grain for population growth, it (Jiang et al., 2015; Ma et al., 2015). When the scale of an agricul- plays a vital role in sustainable social development. After the tural oasis exceeds the carrying capacity of water resources, the stability of an agricultural oasis will be challenged, inducing severe ⇑ Corresponding author. ecological and environmental problems (Lu et al., 2003; Zhang E-mail address: [email protected] (W. Song). et al., 2003). The decline of several ancient agricultural oasis http://dx.doi.org/10.1016/j.pce.2015.08.006 1474-7065/Ó 2015 Elsevier Ltd. All rights reserved. W. Song, Y. Zhang / Physics and Chemistry of the Earth 89–90 (2015) 46–55 47 civilizations (e.g. ancient Babylon) is partly related to the irrational the driving forces behind them using a panel data model. To be expansion of agricultural oases. Therefore, examining the changes specific, the aims of this paper are to: (1) examine the spatial–tem- in agricultural oases and discerning the driving forces behind them poral patterns of agricultural oasis changes in HRB from 1986 to are urgently needed for controlling irrational expansion of agricul- 2011; (2) identify the conclusive factors driving agricultural oasis tural oases. changes; and (3) discuss the feasible policies controlling the irra- Currently, research related to oasis change has focused on four tional expansion of agricultural oasis. aspects: analyzing the land use patterns in oasis agricultural region (Bai et al., 2014; Guo et al., 2008; Hu and Li, 2014; Wang et al., 2. Study area and data sources 2014), discerning the relationship between agricultural oasis change and water resources (Misak et al., 1997; Siebert et al., 2.1. Study area 2007), assessing the ecological effects of agricultural oasis changes (Su et al., 2007; Zhang et al., 2014), and discussing the suitable HRB is located in northwestern China (38°N–42°N, 98°E–101°E), scale of an agricultural oasis (Ling et al., 2013). Although great covering an area over 143.29 thousand kilometers (Fig. 1). HRB is a efforts have been made in the field of oasis change, less attention typical arid region in China. The annual average precipitation is has been paid to identify the factors driving oasis change. In the about 37 mm, 45 mm and 55 mm according to the monitoring limited literature that analyzes the driving forces of agricultural result of local meteorological stations of Ejin, Guaizihu and Dingxin oasis change, a qualitative analysis has been frequently adopted in HRB, while the annual average evaporation exceeded 3000 mm but it cannot accurately identify the key driving forces. (Xiao et al., 2015). To fill the knowledge gap, we examined the changes in the agri- The Heihe River is the second longest inland river in the arid cultural oasis in the Heihe River Basin (HRB), the second largest region of northwestern China. The total length of the Heihe River inland river basin in Northwest China, and quantitatively discerned reaches 821 km (Huai et al., 2014). According to the location of Fig. 1. The location and land use patterns of the Heihe River Basin in 1986. 48 W. Song, Y. Zhang / Physics and Chemistry of the Earth 89–90 (2015) 46–55 Table 1 Selected factors driving agricultural oasis expansion and their connotations. Driving forces Connotation Rural labor force Number of rural population whose age is between 16 years old and 60 years old and frequently participate agricultural production Agricultural machinery The sum of agricultural machinery power, including cultivation machinery, irrigation and drainage machinery, harvest machinery, farm transporting mechanism etc. Irrigation ratio The area ratio of irrigated cultivated land to total cultivated land Plantation structure The ratio of the grain-sown area to agricultural crop sown area Grain yield per unit The yield of grain crop per unit areas of land cultivation Annual precipitation The total precipitation in a year Annual temperature The average temperature in a year Grain-for-green policy A dummy variable. Before grain-for-green policy is launched, it is valued as 0. After grain-for-green policy is launched, it is valued as 1 hydrometric stations of Yingluoxia and Zhengyixia, the Heihe River agricultural machinery has been utilized in agricultural produc- is divided into upper, middle and lower reaches. The upper reaches tion. The use of agricultural machinery can substitute the rural of HRB are runoff formation areas where cold desert accounted for labor force to some degree, and thus influences the scale of an agri- 22% of the total area. The middle reaches of HRB are runoff-using cultural oasis. Here, we selected the input of agricultural machin- areas where most of the agricultural oasis, population and GDP ery per unit as an independent variable. (gross domestic product) are concentrated. The lower reaches of An agricultural oasis exists in arid or semi-arid regions where HRB are a runoff-fade area with a huge evaporation capacity. the water resource is a vital limiting factor (Jin et al., 2014). The The oasis strip in HRB plays a vital ecological role in northwest- abundance or shortage of water resources could determine the ern China. In past decades, with the continuous expansion of the scale of the agricultural oasis to some degree.